Most portable devices, with an electronic display unit for displaying various information relating to the operation of the device, also incorporate a clock. Usually the time is shown on a part of the display, either as digits or as images in the form of analog clock hands.
However, many people prefer watches with mechanical clock hands to digital display systems. Even today with the currently available sophisticated digital displays, most of the wrist watches sold are provided with mechanical clock hands. However, in a portable device whose main purpose is not showing the time, mechanical clock hands will obstruct the view when the display unit is showing other information than the time.
Combined digital displays and mechanical hands are known per see. See for example EP 1046086, disclosing a watch with overlapping, separately driven mechanical and digital displays. However, in a timepiece it is not a problem that the clock hands are visible at all times.